Ancient stromatolite reefs

Northern Canada possesses some of the best preserved examples of Proterozoic reefs and other carbonates anywhere in the world .[Precambrian pinnacle reef, NWT ]

Ancient fossilized strata of stomatolites at Steep Rock Iron Mine Steep Rock Stromatolites, Canada (right). The Canadian shield boasts one of the earth's oldest known rock formations [Acasta Gneisses] and three of the world's earliest known Archaean stromatolite formations: Steep Rock Lake and Red Lake in Ontario, and Yellowknife in the Northwest Territories.

Originating over 3 billion years ago, stromatolites are the oldest known fossils. Fossilized stromatolites were laid down by colonial structures built by photosynthetic Cyanobacteria and associated microbes. The Cyanobacteria, also called 'blue-green algae', were responsible for the creation of earth's oxygen atmosphere. These organisms are prokaryotic – cells lacking a cellular nucleus – and thrived in warm aquatic environments, building reefs much as coral does today. Domed columns are typical, and the fossilized structures were quite extensive. Cyanobacteria were the dominant lifeform on Earth for over 2 billion years.

Today stromatolites are nearly extinct, living a precarious existence in only a few localities worldwide – the most famous location is Shark Bay in Western Australia. _______________________________________________________________________

Precambrian stromatolites of the 1.3 Ga Siyeh Formation in Glacier National Park (left)

"The centres of many stromatolites in the Siyeh Formation are concave downward rather than domed upward, as if they have collapsed. This may, indeed, have happened. The region lay close to the edge of the continent, where frequent earthquakes would have shaken the stromatolites, perhaps damaging them in this way." Source

NW Ontario, Canada contains the Archean Steep Rock carbonate platform, noted as one of the best-exposed and preserved platforms of this age on the planet: Archaean Carbonate Platform stromatolite reef / Archaean stromatolite reef

Stromatolite in ferruginous chert-carbonate unit, Kakabeka Falls Carbonate Chert Picture.

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More images of fossilized stromatolite reefs: Gunflint formation stromatolites on Canadian shore of Lake Superior / exhumed stromatolites 1.8 Ga near Great Slave Lake, Canada / close-up of Great Slave Lake stromatolites / Siyeh Formation in Glacier National Park / bioherm of intertidal columnar stromatolites / domal stromatolites / Petrified Springs Reef near Saratoga Springs / Petrified Springs "Lion" / Lykins Formation / Table Head Group, Nfld, Canada / Ordovician St. George Group, Nfld / patch reef Middle Cambrian, Nfld / Durness Group, Scotland / Johnnie formation, California, 65 Ma / stromatolite reef Auvergne, France and close up of fossilized stromatolite / fossilized stromatolite reef in Mungok Ri, Korea / close-up of a reef